U.S. patent application number 13/256430 was filed with the patent office on 2012-01-05 for dividing wall distillation columns for production of high-purity 2-ethylhexanol and fractionation method using same.
Invention is credited to Jong Ku Lee, Sung Kyu Lee, Joon Ho Shin.
Application Number | 20120004473 13/256430 |
Document ID | / |
Family ID | 43009504 |
Filed Date | 2012-01-05 |
United States Patent
Application |
20120004473 |
Kind Code |
A1 |
Lee; Sung Kyu ; et
al. |
January 5, 2012 |
DIVIDING WALL DISTILLATION COLUMNS FOR PRODUCTION OF HIGH-PURITY
2-ETHYLHEXANOL AND FRACTIONATION METHOD USING SAME
Abstract
There are provided a dividing wall distillation column for
producing high-purity 2-ethyl hexanol, and a fractional
distillation method using the same. The dividing wall distillation
column includes a condenser, a reboiler and a main column having a
dividing wall. Here, the main column is divided into a column-top
zone, an upper feed zone, an upper outflow zone, a lower feed zone,
a lower outflow zone and a column-bottom zone. Also, a crude
2-ethyl hexanol raw material (F) flows in a middle inflow plate NR1
in which the upper feed zone and the lower feed zone come in
contact with each other, a low boiling point component (D) flows
out from the column-top zone, a high boiling point component (B)
flows out from the column-bottom zone, and a middle boiling point
component (S) flows out through a middle outflow plate NR2 in which
the upper outflow zone and the lower outflow zone come in contact
with each other. In this case, the middle boiling point component
is 2-ethyl hexanol. Accordingly, since one distillation column can
be used to realize the same effect as that obtained from the use of
two distillation columns, the dividing wall distillation column can
have an effect of reducing the costs of equipment to produce
high-purity 2-ethyl hexanol, as well as an energy-reducing effect,
compared to a conventional process system.
Inventors: |
Lee; Sung Kyu; (Daegu,
KR) ; Lee; Jong Ku; (Daejeon, KR) ; Shin; Joon
Ho; (Daejeon, KR) |
Family ID: |
43009504 |
Appl. No.: |
13/256430 |
Filed: |
March 19, 2010 |
PCT Filed: |
March 19, 2010 |
PCT NO: |
PCT/KR2010/001725 |
371 Date: |
September 13, 2011 |
Current U.S.
Class: |
568/913 ;
202/158 |
Current CPC
Class: |
B01D 3/14 20130101; C07C
31/125 20130101; C07C 29/80 20130101; C07C 31/125 20130101; C07C
29/80 20130101; B01D 3/141 20130101 |
Class at
Publication: |
568/913 ;
202/158 |
International
Class: |
C07C 29/80 20060101
C07C029/80; B01D 3/14 20060101 B01D003/14 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 19, 2009 |
KR |
10-2009-0023464 |
Mar 19, 2010 |
KR |
10-2010-0024649 |
Claims
1. A dividing wall distillation column comprising a condenser, a
reboiler and a main column having a dividing wall, wherein the main
column is divided into a column-top zone, an upper feed zone, an
upper outflow zone, a lower feed zone, a lower outflow zone and a
column-bottom zone, a crude 2-ethyl hexanol raw material flows in a
middle inflow plate in which the upper feed zone and the lower feed
zone come in contact with each other, a low boiling point component
flows out from the column-top zone, a high boiling point component
flows out from the column-bottom zone, and a middle boiling point
component flows out through a middle outflow plate in which the
upper outflow zone and the lower outflow zone come in contact with
each other, and the middle boiling point component is 2-ethyl
hexanol.
2. The dividing wall distillation column according to claim 1,
wherein the raw material has a 2-ethyl hexanol content of 90% by
weight or more.
3. The dividing wall distillation column according to claim 1,
wherein the number of plates provided respectively in the
column-top zone, the upper feed zone, the upper outflow zone, the
lower feed zone, the lower outflow zone and the column-bottom zone
is in a range of 80 to 145% of a theoretical plate number, as
calculated from a distillation curve.
4. The dividing wall distillation column according to claim 1,
wherein a length of the dividing wall is determined according to
the total theoretical plate number in the upper feed zone and the
lower feed zone.
5. The dividing wall distillation column according to claim 1,
wherein a length of the dividing wall is in a range of 30 to 85% of
the total theoretical plate number in the column-top zone, the
upper feed zone, the lower outflow zone and the column-bottom zone,
as calculated from the distillation curve.
6. The dividing wall distillation column according to claim 1,
wherein a temperature of the column-top zone is in a range of 75 to
85.degree. C. at a pressure of 16.671 kPa.
7. The dividing wall distillation column according to claim 1,
wherein a temperature of the column-bottom zone is in a range of
145 to 160.degree. C. at a pressure of 16.671 kPa.
8. The dividing wall distillation column according to claim 1,
wherein a temperature of the middle outflow plate, which is
provided in a position where the upper outflow zone and the lower
outflow zone come in contact with each other, and from which the
middle boiling point component flows out, is in a range of 130 to
140.degree. C. at a pressure of 16.671 kPa.
9. The dividing wall distillation column according to claim 1,
wherein the temperature of the column-top zone is in a range of a
lower temperature limit (T.sub.1.alpha.) to an upper temperature
limit (T.sub.2.alpha.), which follows the following Equation 1,
when the pressure is out of a pressure of 16.671 kPa: Lower limit:
T.sub.1.alpha.=114.5099*P.sup.0.2439 Upper limit:
T.sub.2.alpha.=123.4949*P.sup.0.2149 Equation 1 (wherein
T.sub.1.alpha. and T.sub.2.alpha. represent temperatures (.degree.
C.); P represents a pressure (kPa), provided that
0.981.ltoreq.P.ltoreq.980.665 and P.noteq.16.671).
10. The dividing wall distillation column according to claim 1,
wherein the temperature of the column-bottom zone is in a range of
a lower temperature limit (T.sub.1.beta.) to an upper temperature
limit (T.sub.2.beta.), which follows the following Equation 2, when
the pressure is out of a pressure of 16.671 kPa: Lower limit:
T.sub.1.beta.=192.1386*P.sup.0.1548 Upper limit:
T.sub.2.beta.=206.5980*P.sup.0.1405 Equation 2 (wherein
T.sub.1.beta. and T.sub.2.beta. represent temperatures (.degree.
C.); P represents a pressure (kPa), provided that
0.981.ltoreq.P.ltoreq.980.665 and P.noteq.16.671).
11. The dividing wall distillation column according to claim 1,
wherein the temperature of the middle outflow plate, which is
provided in a position where the upper outflow zone and the lower
outflow zone come in contact with each other, and from which the
middle boiling point component flows out, is in a range of a lower
temperature limit (T.sub.1.chi.) to an upper temperature limit
(T.sub.2.chi.), which follows the following Equation 3, when the
pressure is out of a pressure of 16.671 kPa: Lower limit:
T.sub.1.chi.=157.7845*P.sup.0.1034 Upper limit:
T.sub.2.chi.=167.6350*P.sup.0.096 Equation 3 (wherein T.sub.1.chi.
and T.sub.2.chi. represent temperatures (.degree. C.); P represents
a pressure (kPa), provided that 0.981.ltoreq.P.ltoreq.980.665 and
P.noteq.16.671).
12. A method of fractionally distilling 2-ethyl hexanol comprising:
producing 2-ethyl hexanol using the dividing wall distillation
column defined in claim 1.
Description
TECHNICAL FIELD
[0001] The present invention relates to a dividing wall
distillation column for producing high-purity 2-ethyl hexanol, and
a fractional distillation method using the same.
BACKGROUND ART
[0002] In general, various source materials such as crude oil are
often present as a mixture of numerous chemicals. Therefore, the
source materials themselves are hardly used in industries, but are
generally separated into respective compounds that are used in
industries. A distillation process is representative of chemical
processes for separating a mixture.
[0003] In general, the distillation process serves to separate the
mixture into two components: a high boiling point component and a
low boiling point component. Therefore, the distillation columns
whose number (n-1) is smaller than the number (n) of components in
the mixture to be separated by 1 are used. That is to say, a
process of separating a three-component mixture has mainly used a
structure in which two distillation columns are continuously
operated on site in conventional distillation industries.
[0004] A conventional distillation process of separating a
three-component mixture is shown in FIG. 1.
[0005] The conventional distillation process uses a two-column
system in which a lowermost boiling point component (D) is
separated in a first column 11, and a middle boiling point
component (S) and a high boiling point component (B) are separated
in a second column 21.
[0006] In a conventional two-column distillation system which is a
conventional process of distilling alcohols, a compositional
profile in a first column is shown in FIG. 2. As shown in FIG. 2,
the middle boiling point component (S) may be generally remixed in
a lower section of the first column. In particular, a compositional
profile in the first column when octanol such as 2-ethyl hexanol is
separated as the middle boiling point component is shown in FIG. 3.
As shown in FIG. 3, it can be seen that the octanol may be remixed
in the lower section of the first column.
[0007] The above-described conventional distillation process can
easily control a composition of a product, but the middle boiling
point component is remixed in the first distillation column.
Therefore, a thermodynamic efficiency in the distillation column is
degraded, resulting in unnecessary consumption of energy.
[0008] In order to solve these problems, much research on a new
distillation structure has been conducted. A representative example
of improving a separation efficiency using a thermally coupled
structure may be a structure of a Petlyuk distillation column as
shown in FIG. 4. The Petlyuk distillation column is arranged in a
structure in which a preliminary separator 12 and a main separator
22 are thermally coupled. Therefore, a low boiling point component
and a high boiling point component are primarily separated in the
preliminary separator, and then flow to a feed plate of the main
separator through a column-top portion and a column-bottom portion
of the preliminary separator. Thereafter, the low boiling point,
middle boiling point, and high boiling point components are
separated in the main separator. This structure has high energy
efficiency since a distillation curve in the Petlyuk distillation
column is similar to an equilibrium distillation curve. However,
the design and operation of a process are not easy, and the balance
of pressure in the distillation column is particularly difficult to
adjust.
[0009] In order to solve the problems regarding the Petlyuk
distillation column, a dividing wall distillation column (DWC) has
been proposed. A thermodynamic aspect of the DWC is similar to that
of the Petlyuk distillation column, but a structural aspect is
different from that of the Petlyuk distillation column in that a
dividing wall is installed in a distillation column to integrate
the preliminary separator of the Petlyuk distillation column in the
main separator. Such a structure is highly advantageous in that
operations are easily performed since the problems regarding the
balance between the preliminary separator of the Petlyuk
distillation column and the main separator are naturally solved and
thus operations are simple, and the investment costs may also be
significantly reduced since two types of distillation columns are
integrated into one.
[0010] Korean Patent No. 080482 filed by and issued to this
applicant discloses a conventional technique associated with the
refinement of 2-ethyl hexanol.
[0011] The above-described technique relates to a purification
method including passing a byproduct, which is generated in a plant
for preparing 2-ethyl hexanol from butylaldehyde through an aldol
condensation reaction and a hydrogenation reaction, through two
multi-stage distillation columns to recover 2-ethyl hexanol and
2-ethylhexyl-2-ethyl hexanoate, characterized in that the byproduct
includes 100 parts by weight of 2-ethyl hexanol, 2 to 6 parts by
weight of a butylaldehyde trimer, 7 to 12 parts by weight of
2-ethylhexyl-2-ethyl hexanoate and 0.01 to 0.3 parts by weight of a
high boiling point component, and the method includes passing the
by-product through a first multi-stage distillation column to
recover 2-ethyl hexanol and distilling a residual substance in a
second multi-stage distillation column under the operating
conditions such as an operating pressure of 980.665 to 9806.650 kPa
and an operating temperature of 150 to 200.degree. C. to recover
2-ethylhexyl-2-ethyl hexanoate.
[0012] Such a technique uses two columns like conventional
processes, but the present invention is quite different from this
technique in that it is not directed to a distillation column
including a dividing wall.
DISCLOSURE
Technical Problem
[0013] In spite of the advantages of the above-mentioned dividing
wall distillation column, the dividing wall distillation column is
hardly installed on site the distillation industry. One important
reason for this is that the dividing wall distillation column is
inflexible in a variation in operating conditions due to the
structural characteristics in which a flow rate of an internally
circulating material cannot be controlled once the dividing wall
distillation column is designed, unlike the Petlyuk distillation
column. That is to say, an exact simulation and a structural
determination are required at the beginning of the design of the
distillation column.
[0014] In recent years, much research on the structure and control
of the dividing wall distillation column has been conducted, but
the details of the design structures and operating conditions of
the dividing wall distillation column such as a position of a feed
plate, setting of a dividing wall section, a position of a plate
for producing a middle boiling point component, a total number of
plates, a distillation temperature and a distillation pressure are
very restrictive in the distillation column.
[0015] Particularly, since the design structures such as a plate
number of the distillation column and a position of a feed plate,
and the operating conditions such as distillation temperature and
pressure should be changed according to the natures of a compound
to be fractionally distilled, it is difficult to use the dividing
wall distillation column.
[0016] Therefore, in order to solve the above-mentioned problems,
reduce energy consumption and the costs of equipment, the present
invention is directed to providing a dividing wall distillation
column having a suitable design to purify 2-ethyl hexanol and a
method of operating the same.
Technical Solution
[0017] Therefore, the present invention is designed to solve the
above problems, and an object of the present invention is to
provide a dividing wall distillation column including a condenser,
a reboiler, and a main column having a dividing wall formed
therein. Here, the main column is divided into a column-top zone,
an upper feed zone, an upper outflow zone, a lower feed zone, a
lower outflow zone and a column-bottom zone. Also, a crude 2-ethyl
hexanol raw material (F) flows in a middle inflow plate NR1 in
which the upper feed zone and the lower feed zone come in contact
with each other, a low boiling point component (D) flows out from
the column-top zone, a high boiling point component (B) flows out
from the column-bottom zone, and a middle boiling point component
(S) flows out through a middle outflow plate NR2 in which the upper
outflow zone and the lower outflow zone come in contact with each
other. In this case, the middle boiling point component is 2-ethyl
hexanol.
[0018] Also, the raw material (F) may have a 2-ethyl hexanol
content of 90% by weight or more.
[0019] In addition, the number of plates provided respectively in
the column-top zone, the upper feed zone, the upper outflow zone,
the lower feed zone, the lower outflow zone and the column-bottom
zone may be in a range of 80 to 145% of a theoretical plate number,
as calculated from a distillation curve.
[0020] Additionally, a length of the dividing wall may be
determined according to the total theoretical plate number in the
upper feed zone and the lower feed zone.
[0021] Also, a length of the dividing wall may be in a range of 30
to 85% of the total theoretical plate number in the column-top
zone, the upper feed zone, the lower outflow zone and the
column-bottom zone, as calculated from the distillation curve.
[0022] In addition, a temperature of the column-top zone may be in
a range of 75 to 85.degree. C. at a pressure of 16.671 kPa.
[0023] Additionally, a temperature of the column-bottom zone may be
in a range of 145 to 160.degree. C. at a pressure of 16.671
kPa.
[0024] Moreover, a temperature of the middle outflow plate NR2,
which is provided in a position where the upper outflow zone and
the lower outflow zone come in contact with each other, and from
which the middle boiling point component (S) flows out, may be in a
range of 130 to 140.degree. C. at a pressure of 16.671 kPa.
[0025] Also, the temperature of the column-top zone may be in a
range of a lower temperature limit (T.sub.1.alpha.) to an upper
temperature limit (T.sub.2.alpha.), which follows the following
Equation 1, when the pressure is out of a pressure of 16.671
kPa:
Lower limit: T.sub.1.alpha.=114.5099*P.sup.0.2439
Upper limit: T.sub.2.alpha.=123.4949*P.sup.0.2149 Equation 1
[0026] (wherein T.sub.1.alpha., and T.sub.2.alpha. represent
temperatures (.degree. C.); P represents a pressure (kPa), provided
that 0.981.ltoreq.P.ltoreq.980.665 and P.noteq.16.671).
[0027] In addition, the temperature of the column-bottom zone may
be in a range of a lower temperature limit (T.sub.1.beta.) to an
upper temperature limit (T.sub.2.beta.), which follows the
following Equation 2, when the pressure is out of a pressure of
16.671 kPa:
Lower limit: T.sub.1.beta.=192.1386*P.sup.0.1548
Upper limit: T.sub.2.beta.=206.5980*P.sup.0.1405 Equation 2
[0028] (wherein T.sub.1.beta. and T.sub.2.beta. represent
temperatures (.degree. C.); P represents a pressure (kPa), provided
that 0.981.ltoreq.P.ltoreq.980.665 and P.noteq.16.671).
[0029] Additionally, the temperature of the middle outflow plate
NR2, which is provided in a position where the upper outflow zone
and the lower outflow zone come in contact with each other, and
from which the middle boiling point component (S) flows out, may be
in a range of a lower temperature limit (T.sub.1.chi.) to an upper
temperature limit (T.sub.2.chi.), which follows the following
Equation 3, when the pressure is out of a pressure of 16.671
kPa:
Lower limit: T.sub.1.chi.=157.7845*P.sup.0.1034
Upper limit: T.sub.2.chi.=167.6350*P.sup.0.096 Equation 3
[0030] (wherein T.sub.1.chi. and T.sub.2.chi. represent
temperatures (.degree. C.); P represents a pressure (kPa), provided
that 0.981.ltoreq.P.ltoreq.980.665 and P.noteq.16.671).
[0031] Another aspect of the present invention provides a method of
fractionally distilling 2-ethyl hexanol. Here, the method includes
producing 2-ethyl hexanol using the above-described dividing wall
distillation column.
Advantageous Effects
[0032] According to the present invention, since one distillation
column can be used to realize the same effect as that obtained from
the use of two distillation columns, the dividing wall distillation
column can have an effect of reducing the costs of equipment to
produce high-purity 2-ethyl hexanol, as well as an energy-reducing
effect, compared to a conventional process system.
DESCRIPTION OF DRAWINGS
[0033] These and other features, aspects, and advantages of
preferred embodiments of the present invention will be more fully
described in the following detailed description, taken accompanying
drawings. In the drawings:
[0034] FIG. 1 is a schematic view showing a conventional
distillation process of separating a three-component mixture.
[0035] FIG. 2 shows a compositional profile in a first column in a
conventional process of distilling alcohols.
[0036] FIG. 3 shows a compositional profile in the first column
when octanol (2-ethyl hexanol) is separated as a middle boiling
point component.
[0037] FIG. 4 is a schematic view showing a structure of a Petlyuk
distillation column
[0038] FIG. 5 is a schematic view showing a structure of a dividing
wall distillation column according to the present invention.
[0039] FIG. 6 is a schematic view showing dividing wall
distillation column described in Comparative Example 1.
[0040] FIG. 7 is a schematic view showing dividing wall
distillation column described in Example 1.
BEST MODE
[0041] Hereinafter, preferred embodiments of the present invention
will be described in detail with reference to the accompanying
drawings.
[0042] The present invention provides a dividing wall distillation
column including a condenser, a reboiler, and a main column having
a dividing wall. Here, the main column is divided into a column-top
zone, an upper feed zone, an upper outflow zone, a lower feed zone,
a lower outflow zone and a column-bottom zone. Also, a crude
2-ethyl hexanol raw material (F) flows in a middle inflow plate NR1
in which the upper feed zone and the lower feed zone come in
contact with each other, a low boiling point component (D) flows
out from the column-top zone, a high boiling point component (B)
flows out from the column-bottom zone, and a middle boiling point
component (S) flows out through a middle outflow plate NR2 in which
the upper outflow zone and the lower outflow zone come in contact
with each other. In this case, the middle boiling point component
is 2-ethyl hexanol.
[0043] A structure of the dividing wall distillation column
according to the present invention is shown in FIG. 5.
[0044] The distillation column of the present invention includes a
condenser 31 and a reboiler 41.
[0045] The condenser serves to condense a mixture in a gas state by
depriving the mixture of evaporation heat. Here, a condenser used
in a conventional chemical engineering system may be used without
limitation.
[0046] The reboiler serves to vaporize a mixture in a liquid state
by providing evaporation heat to the mixture. Here, a reboiler used
in a conventional chemical engineering system may be used without
limitation.
[0047] The main column 1 may be mainly divided into 6 sections.
[0048] The column-top zone 100 refers to an upper section of the
main column that does not have a dividing wall installed
therein.
[0049] The upper feed zone 200 is one of sections divided by the
dividing wall, and is a sub-section arranged above a stream of an
inflow material (raw material).
[0050] The upper outflow zone 300 is one of sections divided by the
dividing wall, and is a sub-section arranged above a stream of an
outflow material.
[0051] The lower feed zone 400 is the other one of the sections
divided by the dividing wall, and is a sub-section arranged under a
stream of the inflow material.
[0052] The lower outflow zone 500 is the other one of the sections
divided by the dividing wall, and is a sub-section arranged under a
stream of the outflow material.
[0053] The column-bottom zone 600 refers to a lower section of the
main column that does not have a dividing wall installed
therein.
[0054] The main column has at least one inflow point and at least
three outflow points.
[0055] A raw material (F) such as crude 2-ethyl hexanol flows in a
middle inflow plate NR1 in which the upper feed zone and the lower
feed zone come in contact with each other, a low boiling point
component (D) flows out from the column-top zone, a high boiling
point component (B) flows out from the column-bottom zone, and a
middle boiling point component (S) flows out through a middle
outflow plate NR2 in which the upper outflow zone and the lower
outflow zone come in contact with each other. In this case, the
middle boiling point component (S) is 2-ethyl hexanol.
[0056] Here, the term "crude 2-ethyl hexanol raw material" refers
to a target material (material to be distilled) used in the
distillation process known in the art, which is a mixture including
2-ethyl hexanol as a main component, and the term "main component"
refers to one component which is included in the largest amount
among the respective components of the mixture. In order to obtain
high-purity 2-ethyl hexanol, the crude 2-ethyl hexanol raw material
preferably has a higher 2-ethyl hexanol content, and in order to
obtain at least 99% by weight of the high-purity 2-ethyl hexanol,
the crude 2-ethyl hexanol raw material preferably has a 2-ethyl
hexanol content of at least 90% by weight.
[0057] According to the present invention, the expression "a middle
boiling point component (S) is 2-ethyl hexanol," means that 2-ethyl
hexanol is not 100% present but substantially present in the crude
2-ethyl hexanol raw material. The expression "2-ethyl hexanol is
substantially present in the crude 2-ethyl hexanol raw material,"
means that a mixture itself is substantially considered 2-ethyl
hexanol, particularly that the mixture includes 2-ethyl hexanol as
a main component and has a higher 2-ethyl hexanol content than a
fed raw material.
[0058] This dividing wall distillation process has lower energy
consumption than a conventional distillation process using two
continuous distillation columns, which may be derived from a
structural difference. In the dividing wall distillation column,
since spaces divided by the dividing wall serve as a preliminary
separator, a composition of a liquid substantially corresponds to
an equilibrium distillation curve due to separation of the high
boiling point component and the low boiling point component, and a
thermodynamic efficiency for separation is good due to suppression
of a remixing effect.
[0059] The upper feed zone and the lower feed zone play a similar
role as the preliminary separator which is operated in a
conventional process (i.e., the upper feed zone and the lower feed
zone may be generally referred to as a preliminary divisional
section). A three-component mixture flowing in the preliminary
divisional section is separated into a low boiling point component
and a high boiling point component. Some of the low boiling point
component and the high boiling point component separated in the
preliminary divisional section flows in the column-top zone and the
column-bottom zone, and some flows back in the upper outflow zone
and the lower outflow zone and is re-distilled.
[0060] The upper outflow zone and the lower outflow zone serve as a
main separator which is operated in a conventional process (i.e.,
the upper outflow zone and the lower outflow zone may be generally
referred to as a main divisional section). Mainly, the low boiling
point component and the middle boiling point component are
separated in an upper portion of the dividing wall of the main
divisional section, and the middle boiling point component and the
high boiling point component are separated in a lower portion of
the dividing wall.
[0061] The low boiling point component is passed through the
column-top zone of the main column and the condenser, and some of
the low boiling point component is then produced into a low boiling
point product (D), and the rest flows back to the column-top zone
of the main column at a liquid flux (LD). The high boiling point
component is passed through the column-bottom zone of the main
column and the reboiler, and some of the high boiling point
component is then produced into a high boiling point product (B),
and the rest flows back to the column-bottom zone of the main
column at a vapor flux (VB).
[0062] The design of a thermally coupled distillation column system
having a dividing wall is based on the design of a conventional
thermally coupled distillation column, and the design of a
distillation column having a minimum number of plates. The
efficiency of the distillation column is maximal when a liquid
compositional distribution of distillation plates in the
distillation column is similar to an equilibrium distillation
curve. Therefore, a minimum-plate distillation system is first
designed on the assumption that a distillation column is operated
under a pre-reflux handling. That is to say, the upper feed zone
and the lower feed zone are designed on the assumption that a
composition of a liquid is identical to that of a raw material in a
raw material feed plate. Also, in the upper outflow zone and the
lower outflow zone, a liquid composition is calculated from the
middle to the column top of the distillation column using a cascade
method for designing an equilibrium composition, starting from a
concentration of the middle boiling point product. In the lower
outflow zone serving as the main separator, a liquid composition is
calculated from the middle to the column bottom of the distillation
column using a cascade method of calculating an equilibrium
composition, starting from a concentration of the middle boiling
point product. Then, the plate number of the upper feed zone and
the lower feed zone, which serve as the preliminary separator, and
the plate number of the upper outflow zone and lower outflow zone,
which serve as the main separator, may be determined from the
distribution of the obtained liquid composition, respectively, by
counting the number of raw material feed plates and the number of
plates having a composition of a product. Here, since the obtained
number of the plates in the distillation column is an ideal
theoretical plate number, the plate number in the distillation
column is preferably in a range of 80 to 145% of the theoretical
plate number, depending on the conventional design standard. When
the plate number is less than 80% of the calculated theoretical
plate number, the low boiling point and high boiling point
components are not easily separated in the preliminary divisional
section, whereas when the plate number exceeds 145%, an
energy-reducing effect is not increased as a section having a
minimum reflux ratio, resulting in an increase in investment
costs.
[0063] Also, a length of the dividing wall installed in the main
column does not have a fixed value, and may be freely varied
according to the kinds and components of a raw material to be
processed. The length of the dividing wall is preferably determined
according to the total theoretical plate number calculated based on
the distillation curves of the upper feed zone and the lower feed
zone.
[0064] In such a dividing wall distillation column, there are
various method of calculating the theoretical plate number and
amount of reflux by determining a spacing of the dividing wall
using an equilibrium distillation curve method on a liquid
composition with the preliminary divisional section and the main
divisional section so as to design an optimal spacing of the
dividing wall. However, the Fenske-Underwood equation is used to
calculate the theoretical plate number according to the present
invention (the Fenske-Underwood equation is widely known to those
skilled in the art).
[0065] The length of the dividing wall is preferably in a range of
30 to 85% of the total theoretical plate number of the column-top
zone, the upper feed zone, the lower outflow zone and the
column-bottom zone, which are calculated based on the distillation
curve. When the length of the dividing wall is less than 30%, some
of the low boiling point component flows down from the preliminary
divisional section, and may be introduced into a product in the
main separator. On the other hand, when the length of the dividing
wall exceeds 85%, it is difficult to maintain smooth equilibrium
flow of liquid/vapor states of the low boiling point/middle boiling
point components and liquid/vapor states of the middle boiling
point/high boiling point components in the distillation column,
which makes it difficult to manufacture a distillation column.
[0066] In the main column, a temperature of the column-top zone is
preferably in a range of 75 to 85.degree. C. at a pressure of
16.671 kPa. When the temperature of the column-top zone is less
than 75.degree. C., the low boiling point component (Light) may
flow down from the preliminary divisional section, which affects
the purity degree of a product. When the temperature of the
column-top zone exceeds 85.degree. C., the high boiling point
component (Heavies) may flow up from the preliminary divisional
section, which affects the purity degree of a product.
[0067] In the main column, a temperature of the column-bottom zone
is preferably in a range of 145 to 160.degree. C. at a pressure of
16.671 kPa. When the temperature of the column-bottom zone is less
than 145.degree. C., a middle boiling point component (2-ethyl
hexanol) flows downwards as a product, which results in a decrease
in production of the product. When the temperature of the
column-bottom zone exceeds 160.degree. C., a high boiling point
component may laterally flow with the middle boiling point
component.
[0068] A temperature of the middle outflow plate NR2, which is
provided in a position where the upper outflow zone and the lower
outflow zone come in contact with each other, and from which the
middle boiling point component (S) flows out, is preferably in a
range of 130 to 140.degree. C. at a pressure of 16.671 kPa. When
the temperature of the middle outflow plate NR2 is less than
130.degree. C., it is difficult to remove a low boiling point
component, whereas, when the temperature of the middle outflow
plate NR2 exceeds 140.degree. C., it is difficult to remove a high
boiling point component, which affects the purity degree of a
product.
[0069] In the main column, the temperature ranges of the column-top
zone, the column-bottom zone and the middle outflow plate NR2 are
based on a pressure of 16.671 kPa (i.e., a pressure somewhat
reduced from a normal pressure). When the distillation column is
operated at a reduced or compressed pressure, the temperature range
may be varied. In general, the higher a pressure is, the higher an
upper temperature limit and a lower temperature limit are.
[0070] In particular, when the column-top zone is out of a pressure
of this pressure range, the temperature of the column-top zone may
be in a range of an upper temperature limit (T.sub.1.alpha.) and a
lower temperature limit (T.sub.2.alpha.), as calculated according
to the following Equation 1:
Lower limit: T.sub.1.alpha.=114.5099*P.sup.0.2439
Upper limit: T.sub.2.alpha.=123.4949*P.sup.0.2149 Equation 1
[0071] (wherein T.sub.1.alpha., and T.sub.2.alpha. represent
temperatures (.degree. C.); P represents a pressure (kPa), provided
that 0.981.ltoreq.P.ltoreq.980.665 and P.noteq.16.671).
[0072] Also, when the column-bottom zone is out of a pressure of
this pressure range, the temperature of the column-bottom zone may
be in a range of an upper temperature limit (T.sub.1.beta.) and a
lower temperature limit (T.sub.2.beta.), as calculated according to
the following Equation 2:
Lower limit: T.sub.1.beta.=192.1386*P.sup.0.1548
Upper limit: T.sub.2.beta.=206.5980*P.sup.0.1405 Equation 2
[0073] (wherein T.sub.1.beta. and T.sub.2.beta. represent
temperatures (.degree. C.); P represents a pressure (kPa), provided
that 0.981.ltoreq.P.ltoreq.980.665 and P.noteq.16.671).
[0074] Additionally, when the middle outflow plate NR2 is out of a
pressure of this pressure range, the temperature of the middle
outflow plate NR2 may be in a range of an upper temperature limit
(T.sub.1.chi.) and a lower temperature limit (T.sub.2.chi.), as
calculated according to the following Equation 3:
Lower limit: T.sub.1.chi.=157.7845*P.sup.0.1034
Upper limit: T.sub.2.chi.=167.6350*P.sup.0.096 Equation 3
[0075] (wherein T.sub.1.chi. and T.sub.2.chi. represent
temperatures (.degree. C.); P represents a pressure (kPa), provided
that 0.981.ltoreq.P.ltoreq.980.665 and P.noteq.16.671).
[0076] As described above, the operation conditions of the dividing
wall distillation column according to the present invention, which
reflect the temperatures of the column-top zone, the column-bottom
zone and the middle outflow plate according to a variation in
pressure, are listed as follows.
TABLE-US-00001 Lower limit Upper limit Pressure = 16.671 kPa
Temperature (.degree. C.) of column-top zone 75 85 Temperature
(.degree. C.) of column-bottom zone 145 160 Temperature (.degree.
C.) of middle outflow plate 130 140 Pressure = 9.807 kPa
Temperature (.degree. C.) of column-top zone 65 75 Temperature
(.degree. C.) of column-bottom zone 135 150 Temperature (.degree.
C.) of middle outflow plate 125 135 Pressure = 29.420 kPa
Temperature (.degree. C.) of column-top zone 85 95 Temperature
(.degree. C.) of column-bottom zone 160 175 Temperature (.degree.
C.) of middle outflow plate 140 150
[0077] As described above, the thermally coupled distillation
column having a dividing wall according to the present invention is
designed to improve the efficiency of the distillation column in a
distillation system for distilling a mixture of three or more
components. Therefore, the distillation column has the same effect
as that obtained from the use of two distillation columns since a
dividing wall is installed in the main column to form spaces, which
have a liquid compositional distribution similar to the
high-efficiency equilibrium distillation system and serve as the
preliminary separator and the main separator.
[0078] Meanwhile, the present invention is directed to a method of
fractionally distilling 2-ethyl hexanol. Here, the method includes
producing 2-ethyl hexanol using the above-described dividing wall
distillation column.
MODE FOR INVENTION
[0079] Hereinafter, the present invention will be described in
further detail with reference to the following Examples. It should
be understood that the descriptions proposed herein are merely
preferable examples for the purpose of illustration only, and not
intended to limit the scope of the invention.
Example 1
[0080] In order to verify the performances of the distillation
systems proposed in the present invention, a dividing-wall
distillation column (DWC) was designed and operated. It was
confirmed that it is possible to obtain a composition of a product
required through an actual operation of the system. Two
conventional distillation columns having no dividing wall were used
in Comparative Example 1, and one distillation column provided with
a dividing wall was used in Example 1. A content of 2-ethyl hexanol
in the raw material was set to 96.09% by weight in both of
Comparative Example 1 and Example 1.
[0081] The distillation columns described in Comparative Example 1
and Example 1 are shown in FIGS. 6 and 7, respectively. Reference
numerals 1 to 8 in FIGS. 6 and 7 represent respective streams as
described in Example 1 and Comparative Example 1.
[0082] The distillation columns of Example 1 and Comparative
Example 1 had theoretical plate numbers as listed in Table 1. In
the distillation column of Example 1, a length of the dividing wall
was set to the theoretical plate number of 54, which corresponded
to 84% of the total theoretical plate number in the column-top
zone, the upper feed zone, the lower outflow zone and the
column-bottom zone.
[0083] The experimental results are listed in the following Tables
2 and 3.
TABLE-US-00002 TABLE 1 Theoretical plate number Example Column-top
zone 100 13 Upper feed zone 200 15 Upper outflow zone 300 37 Lower
feed zone 400 6 Lower outflow zone 500 24 Column-bottom zone 600 12
Comparative First column 33 Example Second column 49
TABLE-US-00003 TABLE 2 Units 1 2 3 4 5 6 7 8 Comparative Condition
Temperature .degree. C. 90.6 50.0 50.0 50.0 162.3 64.9 64.9 152.1
Example Pressure kPa 490.333 16.671 16.671 16.671 490.333 24.517
24.517 49.033 Flow rate kg/hr 11262.7 2761.0 131.0 310.0 10821.7
8509.3 10461.3 360.4 Composition H.sub.2O wt % 1.20 8.53 82.37 8.53
0.02 0.02 0.02 0.00 Light 1.58 49.48 17.64 49.48 0.01 0.01 0.01
0.00 2-EH 96.09 32.72 0.00 32.72 99.11 99.76 99.76 80.39 Heavies
1.13 9.27 0.00 9.27 0.86 0.21 0.21 19.61 Example Condition
Temperature .degree. C. 90.6 50.0 50.0 50.0 135.0 153.0 -- --
Pressure kPa 490.333 16.671 16.671 16.671 24.517 39.227 -- -- flow
rate kg/hr 11262.7 7460.0 121.0 320.0 10461.3 360.4 -- --
Composition H.sub.2O 1.20 8.53 82.37 8.53 0.02 0.00 -- -- Light wt
% 1.58 49.48 17.64 49.48 0.01 0.00 -- -- 2-EH 96.09 32.72 0.00
32.72 99.76 80.39 -- -- Heavies 1.13 9.27 0.00 9.27 0.21 19.61 --
-- * 2-EH: 2-ethyl hexanol
TABLE-US-00004 TABLE 3 Comparative Example Reduction Reduction
First Second (.times.10.sup.7 rate Total column column Example
KJ/hr) (%) Energy 1.68 0.54 1.14 1.11 0.57 34.0 consump- tion
(.times.10.sup.7 KJ/hr)
[0084] As described in Example 1, it was revealed that 99% by
weight of the high-purity 2-ethyl hexanol was effectively recovered
due to suppression of the remixing effect and an increase in
separation efficiency. An additional recycling process of refining
2-ethyl hexanol is not required due to an increase in purity degree
of the product, thereby improving the productivity. The inventive
DWC (one column and two heat exchangers) was much less expensive
than the conventional distillation columns (two columns and four
heat exchangers) in an aspect of the investment costs.
[0085] A reduction rate of energy was highly decreased by
approximately 34.0%, compared to the conventional distillation
columns.
[0086] The present invention has been described in detail. However,
it should be understood that the detailed description and specific
examples, while indicating preferred embodiments of the invention,
are given by way of illustration only, since various changes and
modifications within the scope of the invention will become
apparent to those skilled in the art from this detailed
description.
* * * * *